As known in the art, a color LCD panel 1 has a two-dimensional array of pixels 10, as shown in FIG. 1. Each of the pixels comprises a plurality of sub-pixels, usually in three primary colors of red (R), green (G) and blue (B). These RGB color components can be achieved by using respective color filters. FIG. 2 illustrates a plan view of the pixel structure in a conventional liquid crystal panel, and FIG. 3 is a cross sectional view of the pixel structure. As shown in FIG. 2, a pixel can be divided into three color sub-pixels 12R, 12G and 12B. In a transflective color LCD panel, each sub-pixel can be divided into a transmissive area and a reflective area (not shown). In general, the color sub-pixel 12R is controlled by a gate line 31 and a data line 21, the color sub-pixel 12G is controlled by the gate line 31 and a data line 22, the color sub-pixel 12B is controlled by the gate line 31 and a data line 23. The gate line 32 is used to control the pixels in the next pixel row and the data line 24 is used to control the color sub-pixel 12R in the next pixel column, for example.
FIG. 3 shows a typical color pixel in a transmissive LCD panel or the transmissive area in a transflective LCD. As shown in FIG. 3, a typical LCD panel 10 has many layers: an upper substrate 52 having a polarizer 42, a color filter 110 and a common electrode layer 60; a lower substrate 50 having a polarizer 40, a device layer 70, a passive layer 80 and a lower electrode layer 60. The device layer 70 typically has a plurality of switching elements such as thin-film transistors for controlling the color sub-pixels, and a plurality of capacitors for charge storage purposes. The lower electrode layer 60 comprises a first sub-pixel electrode 62, a second sub-pixel electrode 64 and a third sub-pixel electrode 66. The first sub-pixel electrode 62, electrically connected to the control elements in the device layer 70 by a via 72, is associated with the color sub-pixel 12R. The second sub-pixel electrode 64, electrically connected to the control elements in the device layer 70 by a via 74, is associated with the color sub-pixel 12G. The third sub-pixel electrode 66, electrically connected to the control elements in the device layer 70 by a via 76, is associated with the color sub-pixel 12B. A liquid crystal layer 90 is disposed between the upper substrate and the lower substrate. A backlight source 150 located on the backside of the LCD panel is used to provide illumination.
As known in the art, the liquid crystal molecules in the liquid crystal layer can be caused to change its bulk structure by the voltage potential across the layer. Depending on the type or the characteristics of a liquid crystal layer, the liquid crystal molecules can be caused to align along a certain direction by the voltage potential between the common electrode 60 and the sub-pixel electrode. When the voltage potential is removed or the voltage on the sub-pixel electrode is turned off, the liquid crystal molecules can become randomly oriented. For simplicity, it is suffice to state that the liquid crystal layer associated with a sub-pixel can be in a light-blocking state or in a light non-blocking state. As shown in FIG. 3, the liquid crystal molecules are aligned along an axis that is perpendicular to the substrates 50 and 52. As such, the liquid crystal layer in all three color sub-pixels 12R, 12G and 12B is in a light non-blocking state. The light beam from the backlight source 150 can sufficiently pass through the liquid crystal layer 90 and the color filter 110 to reach a viewer's eyes. If the light beam from the backlight source 150 is white and containing three primary color components of R, G and B, the light component passed through the red color filter R in the sub-pixel 12R is red, the light component passed through the green color filter G in the sub-pixel 12G is green, and the light component passed through the blue color filter B in the sub-pixel 12B is blue.
As the light beam passes through the color filter 110, a substantial part of the light beam is absorbed in the color filter 110. It is thus desirable to provide a liquid crystal display panel wherein the absorption of the backlight beam can be reduced.